machovec



March 3l, 1959 F. J. MAcHovEc 2,879,629

` LAWN MowER SHARPENER Filed sept. 2o, 1957 2 sheets-sheet 1 #een Cl Mea/avec;

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March 31, 1959 F. J. MACHOVC i 2,879,629

LAWN MOWER SHARPENER Filed Sept. 20, 195'? /2 Sheets-Sheet 2 l $.72@ I M I'lllllmlL-J 32 44 2p 4....- ...(1543 lle .F/,Qao Cl.' Mamans@ United States Patent O f' LAWN MOWER SHARPENER Fred J. Machovec, Pasadena, Calif.

Application September 20, 1957, Serial No. 685,334

the track means, and a grinding wheel mounted on the y carriage and engageable with the lawn mower blade or blades to sharpen same.

The carriage includes a base on which the grinding wheel is mounted, and includes a sub-base which carries the base and which includes track follower means in engagement with the track means, the base being pivotally mounted on the sub-base in such a manner that the grinding wheel may be raised vand lowered relative to the lawn-mower positioning means by adjusting the angular position of the base relativeto the sub-base. With this construction, the lawn-mower positioning means and the base are adjusted relative to the'supporting structure and the sub-base, respectively, in such a manner as to properly position the grinding wheel relative to the lawn mower blade to be sharpened, whether this blade be a reel knife, a cutter-bar knife, or the like. The blade is then sharpened by moving the carriage along the track means with the grinding Wheel yin engagement with the blade until the grinding wheel has traversed the full length of the blade.

With the foregoing lawn mower Sharpener of my prior patent, it sometimes'develops that the initial locations of the lawn-mower positioning means and the base of the carriage'fdo not result in' sharpening the particular blade being processed uniformly from one end thereof to the other, particularly if such blade is warped. Consequently, the relative locations of the blade and the grinding-wheel must be readjusted to obtain a deeper cut, which may be accomplished either by adjustment of the lawn-mower positioning means to move the blade being sharpened closer to the track means, or by vadjustment of the angular position of the base relative to the sub-base to move the grinding wheel closer to the blade being sharpened. The tirstadjustment is an extremely tedious one and is diicult to accomplish without throwing the blade being sharpened out of parallelism with the path of movement of the carriage along the track means. The second adjustment inherently results in downward movement of thefgrinding wheel relative to the blade being sharpened, in addition to movement thereof toward suchblade, because of the pivotal connection between the base and the sub-base, and thus changes the angle at which the blade is ground, which is undesirable.

Ay primary object of the present invention is to overcome the foregoing dilculties encountered with the lawn 2,879,629 Patented Mar. 3l, 1959 ICC mower Sharpener of my prior patent by providing for grlnding-wheel movement toward and away from the lawn-mower positioning means without any change in the angular relationship between the grinding wheel and the blade being sharpened. Thus, with the present invention,A once the location of the lawn-mower positioning means relative to the supporting structure and the angular location of the base of the carriage relative to the sub-base thereof have been adjusted properly, the grinding Wheel may be moved closer to the blade being sharpened to obtain a greater depth of cut than initially provided for without changing the angular relationship between the grinding wheel and the blade, which is an important feature.

Another object of the invention is to provide a carriage structure for accomplishing the foregoing which includes an upper carriage member forming the base of the carriage of my prior patent and which includes intermediate and lower carriage members forming the subbase of my prior carriage, the upper carriage member being pivotally connected to the intermediate carriage member and the intermediate carriage member being reciprocable relative to the lower carriage member in a direction transversely of the track means and toward and away from the lawn-mower positioning means. Thus, once the locations of the lawn-mower positioning means relative to the supporting structure and the upper carriage member relative to the intermediate carriage member have been adjusted, the location of the upper and intermediate carriage members relative to the lower carriage member may be adjusted to move the grinding wheel closer to the blade being sharpened without changing the predetermined angle at which such blade is to be ground.

Another important object ofthe invention is to provide a lawn mower Sharpener wherein the axis of rotation of the grinding wheel may be rotated about an axis which extends transversely of the track means. With this construction, the grinding wheel may be operated with its axis of rotation generally horizontal, or it may beoperated with its axis of rotation generally vertical. The latter position of the axis of rotation of the grinding wheel permits flat grinding of the stationary blade or bed knife of the lawn mower, which is an important feature.

Another object is to movably mount the grinding wheel in such a manner that it can be driven by a single belt in either of the positions mentioned for the axis of rotation of the grinding wheel, the runs of the belt being parallel when the axis of rotation of the grinding wheel is generally horizontal, and the runs of the belt being crossed when the axis of rotation of the grinding wheel is generally vertical. A related object is to provide means for maintaining constant belt tension for either position of the axis of rotation of the grinding wheel.

The foregoing objects, advantages, features and results of the present invention, together with other objects, advantages, features and results thereof which will be evident to those skilled in the lawn mower sharpening art in the light of the present disclosure, may be attained with the exemplary embodiment of the invention de scribed in detail hereinafter and illustrated in the acstituting the present invention.

Fig. 5 is an enlarged, fragmentary sectional view taken along the -arrowed line `5-5 of Fig. 2';

Fig. 6 is a bottom plan view of a part of the carriage of the invention;

Fig. 7 is Van exploded perspective view of a sub-base of the carriage;

Fig. `8 lis a fragmentary perspective view of the lawn mower Sharpener of the invention in use to hollow grind a lawn mower bed knife; and

Fig. 19 is a fragmentary perspective view of the lawn mowery Sharpener of the vinvention in use to at grind a bed knife.

4'In .the drawings and in the description which follows, only those portions ofthe structure of the lawn mower Sharpener of my prior .patent are disclosed which are necessary 'to an understanding of the 4improvements con- Consequently, reference is hereby made to my prior patent for a complete disthe invention not specifically disclosed herein.

Referring `particularly to Fig. 1` of the drawings, the

lawn mower Sharpener is designated generally by the numeral 10 and includes a track means 12 which preferably comprises two substantially parallel tracks '14 in the form of cylindrical `rods the axes of which are disposed in substantially vthe same horizontal plane. The tracks 14 extend across the front yof the lawn mower Sharpener 10 and located rearwardly of and alongside the tracks is a lawn-mower positioning means 16, which may carry either a lawn mower 18 from which the cutter bar has been removed, as shown in Fig. l, or which may carry alawn `mower cutter bar 20, as shown in Fig. 8. The lawn-mower positioning means 16 is adjustable transversely of 'the tracks 14 to properly locate the lawn mower 18, or its cutter ybar 20, relative to the tracks. Reference is hereby made to my aforementioned prior patent for a more complete disclosure of the manner in which the positioning means 16 is adjusted and the manner yin lwhich it holds the lawn mower 1S, or the cutter bar 20, such structure, per se, forming no part of the present invention.

Movable along the tracks 14 4of the lawn mower sharpener 10 is a carriage 30 which includes an upper carriage member lor base 32 and which includes a sub-base comprising an intermediate carriage member 34 and a. Ilower carriage member 36. The upper carriage member 32 is 'pivotally mounted on the sub-base formed by the carriage members 34 and '36, or, more accurately, is

`pivota-llymounted on the intermediate carriage member 34, the upper carriage member being pivotable about a substantially horizontal axis which is substantially parallel tothe tracks 14 and which 'is located adjacent the edge ofthe upper carriage member most remote from the positioning `means 16. vThis pivotal connection between ;the upper carriage member 32 and the intermediate carriage member 34 is provided by two balls 38 each'seated in an opening 40 in the upper carriage member-and anopening 42 in the intermediate carriage member, asbest shown in Fig. 5. The upper and intermediate carriage members 32 and 34 are held in assembled relation by a bolt 44 which extends through these carriage members on the pivot axis provided by the balls 38, the .carriagemembers 32 and `34 being biased toward each other by a compression spring 46 which vencrcles the bolt 4.4 and which ishxed relative'to the bolt `at one end and relative to the .carriage member 34 `atits other end.

The angular positionof the upper carriage member 32 relative to the intermediate carriage member 34 may be adjusted `by means of ascrew .48 threadedly connected to the upper carriage member 32 and bearing against the intermediate carriage member 34, this screw being provided with a crank 50 at its upper end. .As will be apparent, byturning Athe crank 50, theangular position of the upper carriage member 32 relative to the intermediate carrage member 34 may be varied to vary the vertical position of a grinding wheel 52 on the upper carriage member 32 relative to the lawn-mower positioning means 16 so as to obtain the desired angular relationship between the grinding wheel and a blade to be sharpened. The manner in which the grinding wheel 52 is mounted on the upper carriage member 32 and the manner in which it is driven will be considered in detail hereinafter.

Considering the lower carriage member 36, it is provided with a track follower means which includes a single roller 54 engageable with the track 14 nearest the lawnmower positioning means 16, and two pairs of oppositely inclined rollers 56 engageable with the other of the tracks i4, all as more fully disclosed in my prior patent. The intermediate and lower carriage members 34 and 36 are provided with pairs of registering grooves 58 which extend transversely of the tracks 14 and toward and away from the lawn-mower positioning means 16, each pair of grooves containing a ball 60. As will be apparent, this construction permits movement of vthe grinding wheel mount formed by the upper carriage member 3 2 and the intermediate carriage member 34 toward and away from -the lawn-mower positioning means 16 in a horizontal plane so as to avoid changing theangular relationship between ithe grinding Wheel 52and a blade being sharpened. As hereinbefore outlined, this avoids any change in the angle at which such 4.blade is ground once the proper angular relation between the upper carriage member 32 and the intermediate carriage member 34 has been established bymeaus ofthe screw 48.

like intermediate .carriage Ylrlerrlber 34 vis vmoved relative to the lower carriage member 36 by an adjusting means 62 which includes a screw 64 threadedly connected ,to =the lower carriage member 36 and bearing againstthe .intermediate carriage member 34, or, more accurately, bearing ragainst a lug 66 on the intermediate carriage member. A ,compression spring 68 encircling the screw 64 acts to bias the intermediate carriage member 34 away ,from the klawn-mower positioning means 16 and serves to prevent rotation of the screw 64 under the influence of vibration, `or the like, by axially loading the threaded connection between such screw and the lower carriage member 36.

Separation of theintermediate and lower carriage members 34 and 36 is prevented -by a bolt 70 which extends through an enlarged hole 72 in the lower carriage member to permit the desired relative movement ofthe carriage members 34 and 3 6, these two carriage members being biased toward each -otherby a compression spring 74 which encirclesthebolt 70 and which is fixed at one end relative to the boltand lat Aits other end relative to the lower carriagemember.

Considering ythe manner .in :which Athe .grinding wheel 52 is rmounted r01x the upper carriage member 432, the grinding wheel is Vcarried by a grinding wheel mount 7.6 which includes a .sleeve ,78for a shaft carrying the grinding wheel. This shaft also carries a driven pulley 82 around which is 4trained an endless belt 84, the latter alsobeing trained around a driving pulley `86 carried by the shaft of an electric motor 8.8` suitably secured to the upper carriage member 32. The sleeve v78 of the grinding wheel mount 7,6;has connected thereto -a shaft 9 0 the axis of which is vperpendicularftothe axis of rotation of the grinding -wheel `S2. 'Ehe K.shaft 90 :projects Vinto ja split sleeve /92 `carried by fa: bracket ,94 suitably Ysecured .to the upper carriagememher :32, the-shaft 90 -being lclamped in thesleeve 92 by.;a ylockingrrneans 96 having the Yform of a screw -adaptedwto clamp the ,splitsleeve 92 around theshaft90.

With the :foregoing grinding :Wheel mount 76, the shaft 90 may be locked in any desired angular position relative Ltoithe sleeve 92to provide various orientations for the axis of rotation of the grinding wheel 52. For example, the shaft 90 may be clamped to the sleeve 92 by the locking means 96 with the axis of rotation of the grinding wheel 52 substantially horizontal and parallel to the tracks 14, thereby permitting hollow grinding of the reel blades of the lawn mower 18, as shown in Fig.v 1, or hollow grinding of the stationary blade of the cutter bar 20, as shown in Fig. 8. Alternatively, the shaft 90 may be rotated through 90 relative to the sleeve 92 to orient the axis of rotation of the grinding w-heel generally vertically. This permits flat grinding of the stationary blade on the cutter bar 20, as shown in Fig.'9 of the drawings.

The shaft 90 is also movable in the sleeve 92 transversely of the tracks 14 and toward and away from the lawn-mower positioning means 16, the shaft 90 being biased toward the positioning means 16 by a compression spring 98 disposed within the sleeve 92 and having one of its ends xed relative to the shaft 90 and the other of its ends xed relative to the sleeve. The spring 98 performs the functions'of maintaining the tension in the belt 84 constant for either the grinding-wheel position shown in Fig. 8, or the position thereof shown in Fig. 9, the runs of the belt being parallel in the former instance and being crossed in the latter. Of course, once the spring 98 has properly tensioned the belt 84 in either of these positions of the grinding wheel 52, the locking means 96 is actuated to clamp the grinding wheel mount 76 in the desired angular position thereof and in the desired fore-and-aft position thereof relative to the lawnmower positioning means 16.

Considering the over-all operation of the invention, the lawn-mower positioning means 16 and the adjusting means provided by the screw 48 are so set as t-o provide the desired relationship between the blade or knife to be sharpened and the grinding wheel 52, it being assumed for the moment that the grinding wheel is in the hollow grinding position illustrated in Figs. 1 and 8. The carriage 30 is then moved along the tracks 14 to grind the blade from one end thereof to the other. If it is found to be necessary to increase the depth of cut for any reason, the adjusting means 62 is then utilized to move the grinding wheel 52 closer to the blade being ground, whereupon the carriage 30 is again moved along the tracks 14 to grind the desired blade. This movement of the grinding wheel 52 toward the blade being ground is accomplished without any necessity for altering the previously set angular relation between the upper carriage member 32 and the intermediate carriage member 34, whereby no change in the angular relationship between the grinding wheel and the blade is produced. Consequently, the grinding wheel 52, in its new position, grinds the blade with the same bevel as originally predetermined by the adjustments of the positioning means 16 and the screw 48, which is an important feature of the invention.

If it is desired to flat grind the bed knife of the lawn mower, instead of hollow grinding it, this may be accomplished readily by releasing the locking means 96, rotating the grinding wheel mount 76 through 90 from the position shown in Fig. 8 to that shown in Fig. 9, and tightening the locking means 96 again, the spring 98 automatically producing the proper tension in the belt 84.

Although an exemplary embodiment of the present invention has been disclosed herein for purposes of illustration, it will be understood that various changes, modications and substitutions may be incorporated in such embodiment without departing from the spirit of the invention as deiined by the claims which follow.

I claim:

l. In a lawn mower sharpener, the combination of: generally horizontal track means; means for positioning a lawn mower to be sharpened alongside said track means; a carriage movable along and carried by said track means, said carriage including upper, intermediate and lower carriage members, said upper carriage member being piv- 6 i otally connected to said intermediate carriage member for movement about a generally horizontal pivot axis paralleling said track means, said intermediate and lower carriage members being provided therein with pairs of registering grooves, which pairs extend transversely of said track means and each of which pairs contains a ball having a diameter exceeding the sum of the depths of said registering grooves ofsuch pair, said intermediate car* riage member being reciprocable relative to said lower carriage member transversely of said track means and toward and away from said lawn-mower positioning means on ysaid balls, there beingl three of'said ball-containing pairs of registering grooves arranges in a triangular pattern to provide three-,point contact between said balls and each of said intermediate and lower carriage members, and said lower carriage member carrying track follower means in engagement' with said track means; adjusting means connected to said upper carriagel member for pivoting said upper carriage member relative to said intermediate carriage member about said pivot axis; adjusting means connected `to said intermediate carriage member for moving said intermediate carriage member transversely of said track means; andta grindingl wheel carried by said upper carriage member. s

2. In a lawn mower sharpener,',the combination of: generally horizontal track means; means for positioning a lawn mower to be sharpened alongside said track means; a carraige movable along and carried by said track means, said carriage including two carriage members provided therein with pairs of registering grooves, which pairs extend transversely of said track means and each of which pairs contains a ball having a diameter exceeding the sum of the depths of said registering grooves of such pair, one of said carriage members being reciprocable relative to the other transversely of said track means and toward and away from said lawn-mower positioning means on said balls, there being three of said ball-containing pairs of registering grooves arranged in a triangular pattern so as to provide three-point engagement between said balls and each of said carriage members, said other carriage member having thereon track follower means in engagement with said track means; adjusting means for moving said one carriage member relative to said other carriage member transversely of said track means; a grinding wheel; and means mounting said grinding wheel on said one carriage member.

3. In a lawn mower sharpener, the combination of: track means; means for positioning a lawn mower to be sharpened alongside said ltrack means; a carriage movable along and carried by said track means, said carriage including a grinding wheel mount which is movable transversely of said track means toward and away from said lawn-mower positioning means; a grinding wheel carried by said grinding wheel mount; a driven pulley carried by said grinding wheel mount and connected to said grinding wheel; a motor carried by said carriage and having a driving pulley thereon, said driven and driving pulleys being spaced apart transversely of said track means; a belt trained over said driving and driven pulleys and extending transversely of said track means in the direction of reciprocatory movement of said grinding wheel mount; and spring means engaging said grinding wheel mount and said carriage and biasing said grinding wheel mount toward said lawn-mower positioning means, whereby said spring means tensions said belt.

4. In a lawn mower sharpener, the combination of: track means; means for positioning a lawn mower component to be sharpened alongside said track means; a carriage movable along and carried by said track means; a grinding wheel mount; means mounting said grinding wheel mount on said carriage for rotation of said grinding wheel mount relative to said carriage about an axis extending transversely of said track means and toward said positioning means and for reciprocation of said grinding wheel mount relative to said carriage in the direction of 7 said axis, ksaid mounting :means includingY .interengageable bearing elements on said grinding wheel .mount and said carriage, respectively; and a grinding wheel carried by said grinding wheelmount.

5. ,In a lawn mower .sha1-planer, the combination. of: track means; means for positioning a lawn mower component to be sharpened alongside said track means; a carriage movable along .and carried yby -said track means; a grinding wheel mount; means mounting said grinding wheel mount on said kcarriage .for rotation of `said grinding wheel mount ,relative to said carriage about an axis extending transversely of .said track means and toward said positioning means, .said .mounting ,means including interengageable bearing elements respectively carried. by said grinding wheel mount land Asaid carriage; means for locking said grinding wheel .mount in various `angular positions relative to lsaid carriage about said axis; and a grindingwheel carried by said grinding wheel .mount and rotatable about an axis perpendicular `to the axis rst mentioned.

6. In a lawn mower sharpener, the combination of: track means; means `,for .positioning a .lawn mower component to be sharpened alongside said track means; .a carriage movable along `and Acarried by said track means, said carriage .including a grinding wheel mount which is rotatable about an axis extending transversely of said track means and which -is reciprocable transversely of said track .meanstoward and away :from .said positioning means inthe direction of said axis; means for locking said grinding wheel mount in various angular positions about said axis; a grinding wheel carried by said grinding Wheel mount .and rotatable about an axis perpendicular to the axis lrst mentioned; and spring means engaging said grinding wheel mount and biasing said grinding wheel mount toward saidpositioning means.

7. A lawn mower Sharpener according to claim 6 including a motor carried by said carriage and having a driving pulley thereon, a driven pulley carried by said grinding wheel mount and connected to said grinding wheel, said driving and driven pulleys being spaced apart transversely of said track means, and a belt trained over said driving and driven pulleys and extending transversely of said track means in the direction of reciprocatory movement of said grinding Wheel mount, whereby said spring means tensions said belt.

References Cited in the file of this patent UNITED STATES PATENTS 384,795 Shoemaker Y..a a June 19, 1888 2,142,669 Carpenter -..t. .1311. 3, 1939 2,718,097 Bradley v.. Sept. 20, 1955 

